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Anytime there is a leak in the transmission system, it is worth pursuing. It is very possible and likely that if the leak is not fixed it will get larger. Also you may run low on fluid without knowing which may further damage the transmission. Furthermore , the transmission fluid that leaks out, may leak onto other components causing damaged.
It is well worth fixing the problem, and having peace of mind when driving.
As far as the timing belt goes, it is suggest that you replace the timing belt at about every 60,000 miles. If you have not change the timing belt in the last 60,000 miles it is time to do so.